diff --git a/encoding/protojson/decode.go b/encoding/protojson/decode.go
index 71c755c..2a60775 100644
--- a/encoding/protojson/decode.go
+++ b/encoding/protojson/decode.go
@@ -52,6 +52,13 @@
 // setting the fields. If it returns an error, the given message may be
 // partially set.
 func (o UnmarshalOptions) Unmarshal(b []byte, m proto.Message) error {
+	return o.unmarshal(b, m)
+}
+
+// unmarshal is a centralized function that all unmarshal operations go through.
+// For profiling purposes, avoid changing the name of this function or
+// introducing other code paths for unmarshal that do not go through this.
+func (o UnmarshalOptions) unmarshal(b []byte, m proto.Message) error {
 	proto.Reset(m)
 
 	if o.Resolver == nil {
diff --git a/encoding/protojson/encode.go b/encoding/protojson/encode.go
index e545feb..73b750a 100644
--- a/encoding/protojson/encode.go
+++ b/encoding/protojson/encode.go
@@ -104,6 +104,13 @@
 // MarshalOptions. Do not depend on the output being stable. It may change over
 // time across different versions of the program.
 func (o MarshalOptions) Marshal(m proto.Message) ([]byte, error) {
+	return o.marshal(m)
+}
+
+// marshal is a centralized function that all marshal operations go through.
+// For profiling purposes, avoid changing the name of this function or
+// introducing other code paths for marshal that do not go through this.
+func (o MarshalOptions) marshal(m proto.Message) ([]byte, error) {
 	if o.Multiline && o.Indent == "" {
 		o.Indent = defaultIndent
 	}
diff --git a/encoding/prototext/decode.go b/encoding/prototext/decode.go
index 77dbe1b..c2f8f28 100644
--- a/encoding/prototext/decode.go
+++ b/encoding/prototext/decode.go
@@ -54,6 +54,13 @@
 // Unmarshal reads the given []byte and populates the given proto.Message using options in
 // UnmarshalOptions object.
 func (o UnmarshalOptions) Unmarshal(b []byte, m proto.Message) error {
+	return o.unmarshal(b, m)
+}
+
+// unmarshal is a centralized function that all unmarshal operations go through.
+// For profiling purposes, avoid changing the name of this function or
+// introducing other code paths for unmarshal that do not go through this.
+func (o UnmarshalOptions) unmarshal(b []byte, m proto.Message) error {
 	proto.Reset(m)
 
 	if o.Resolver == nil {
diff --git a/encoding/prototext/encode.go b/encoding/prototext/encode.go
index dece229..41e5c77 100644
--- a/encoding/prototext/encode.go
+++ b/encoding/prototext/encode.go
@@ -102,6 +102,13 @@
 // MarshalOptions object. Do not depend on the output being stable. It may
 // change over time across different versions of the program.
 func (o MarshalOptions) Marshal(m proto.Message) ([]byte, error) {
+	return o.marshal(m)
+}
+
+// marshal is a centralized function that all marshal operations go through.
+// For profiling purposes, avoid changing the name of this function or
+// introducing other code paths for marshal that do not go through this.
+func (o MarshalOptions) marshal(m proto.Message) ([]byte, error) {
 	var delims = [2]byte{'{', '}'}
 
 	if o.Multiline && o.Indent == "" {
diff --git a/internal/cmd/generate-types/proto.go b/internal/cmd/generate-types/proto.go
index 8ea491b..ded7720 100644
--- a/internal/cmd/generate-types/proto.go
+++ b/internal/cmd/generate-types/proto.go
@@ -413,18 +413,18 @@
 }
 
 var protoSizeTemplate = template.Must(template.New("").Parse(`
-func sizeSingular(num protowire.Number, kind protoreflect.Kind, v protoreflect.Value) int {
+func (o MarshalOptions) sizeSingular(num protowire.Number, kind protoreflect.Kind, v protoreflect.Value) int {
 	switch kind {
 	{{- range .}}
 	case {{.Expr}}:
 		{{if (eq .Name "Message") -}}
-		return protowire.SizeBytes(sizeMessage(v.Message()))
+		return protowire.SizeBytes(o.size(v.Message()))
 		{{- else if or (eq .WireType "Fixed32") (eq .WireType "Fixed64") -}}
 		return protowire.Size{{.WireType}}()
 		{{- else if (eq .WireType "Bytes") -}}
 		return protowire.Size{{.WireType}}(len({{.FromValue}}))
 		{{- else if (eq .WireType "Group") -}}
-		return protowire.Size{{.WireType}}(num, sizeMessage(v.Message()))
+		return protowire.Size{{.WireType}}(num, o.size(v.Message()))
 		{{- else -}}
 		return protowire.Size{{.WireType}}({{.FromValue}})
 		{{- end}}
diff --git a/proto/decode.go b/proto/decode.go
index 1282147..4974b16 100644
--- a/proto/decode.go
+++ b/proto/decode.go
@@ -63,12 +63,15 @@
 	return o.unmarshal(in.Buf, in.Message)
 }
 
+// unmarshal is a centralized function that all unmarshal operations go through.
+// For profiling purposes, avoid changing the name of this function or
+// introducing other code paths for unmarshal that do not go through this.
 func (o UnmarshalOptions) unmarshal(b []byte, m protoreflect.Message) (out protoiface.UnmarshalOutput, err error) {
 	if o.Resolver == nil {
 		o.Resolver = protoregistry.GlobalTypes
 	}
 	if !o.Merge {
-		Reset(m.Interface()) // TODO
+		Reset(m.Interface())
 	}
 	allowPartial := o.AllowPartial
 	o.Merge = true
@@ -105,7 +108,7 @@
 func (o UnmarshalOptions) unmarshalMessageSlow(b []byte, m protoreflect.Message) error {
 	md := m.Descriptor()
 	if messageset.IsMessageSet(md) {
-		return unmarshalMessageSet(b, m, o)
+		return o.unmarshalMessageSet(b, m)
 	}
 	fields := md.Fields()
 	for len(b) > 0 {
diff --git a/proto/encode.go b/proto/encode.go
index 456bfda..7b47a11 100644
--- a/proto/encode.go
+++ b/proto/encode.go
@@ -134,6 +134,9 @@
 	return o.marshal(in.Buf, in.Message)
 }
 
+// marshal is a centralized function that all marshal operations go through.
+// For profiling purposes, avoid changing the name of this function or
+// introducing other code paths for marshal that do not go through this.
 func (o MarshalOptions) marshal(b []byte, m protoreflect.Message) (out protoiface.MarshalOutput, err error) {
 	allowPartial := o.AllowPartial
 	o.AllowPartial = true
@@ -206,7 +209,7 @@
 
 func (o MarshalOptions) marshalMessageSlow(b []byte, m protoreflect.Message) ([]byte, error) {
 	if messageset.IsMessageSet(m.Descriptor()) {
-		return marshalMessageSet(b, m, o)
+		return o.marshalMessageSet(b, m)
 	}
 	// There are many choices for what order we visit fields in. The default one here
 	// is chosen for reasonable efficiency and simplicity given the protoreflect API.
diff --git a/proto/messageset.go b/proto/messageset.go
index b6b3de5..1d692c3 100644
--- a/proto/messageset.go
+++ b/proto/messageset.go
@@ -13,24 +13,24 @@
 	"google.golang.org/protobuf/reflect/protoregistry"
 )
 
-func sizeMessageSet(m protoreflect.Message) (size int) {
+func (o MarshalOptions) sizeMessageSet(m protoreflect.Message) (size int) {
 	m.Range(func(fd protoreflect.FieldDescriptor, v protoreflect.Value) bool {
 		size += messageset.SizeField(fd.Number())
 		size += protowire.SizeTag(messageset.FieldMessage)
-		size += protowire.SizeBytes(sizeMessage(v.Message()))
+		size += protowire.SizeBytes(o.size(v.Message()))
 		return true
 	})
 	size += messageset.SizeUnknown(m.GetUnknown())
 	return size
 }
 
-func marshalMessageSet(b []byte, m protoreflect.Message, o MarshalOptions) ([]byte, error) {
+func (o MarshalOptions) marshalMessageSet(b []byte, m protoreflect.Message) ([]byte, error) {
 	if !flags.ProtoLegacy {
 		return b, errors.New("no support for message_set_wire_format")
 	}
 	var err error
 	o.rangeFields(m, func(fd protoreflect.FieldDescriptor, v protoreflect.Value) bool {
-		b, err = marshalMessageSetField(b, fd, v, o)
+		b, err = o.marshalMessageSetField(b, fd, v)
 		return err == nil
 	})
 	if err != nil {
@@ -39,7 +39,7 @@
 	return messageset.AppendUnknown(b, m.GetUnknown())
 }
 
-func marshalMessageSetField(b []byte, fd protoreflect.FieldDescriptor, value protoreflect.Value, o MarshalOptions) ([]byte, error) {
+func (o MarshalOptions) marshalMessageSetField(b []byte, fd protoreflect.FieldDescriptor, value protoreflect.Value) ([]byte, error) {
 	b = messageset.AppendFieldStart(b, fd.Number())
 	b = protowire.AppendTag(b, messageset.FieldMessage, protowire.BytesType)
 	b = protowire.AppendVarint(b, uint64(o.Size(value.Message().Interface())))
@@ -51,12 +51,12 @@
 	return b, nil
 }
 
-func unmarshalMessageSet(b []byte, m protoreflect.Message, o UnmarshalOptions) error {
+func (o UnmarshalOptions) unmarshalMessageSet(b []byte, m protoreflect.Message) error {
 	if !flags.ProtoLegacy {
 		return errors.New("no support for message_set_wire_format")
 	}
 	return messageset.Unmarshal(b, false, func(num protowire.Number, v []byte) error {
-		err := unmarshalMessageSetField(m, num, v, o)
+		err := o.unmarshalMessageSetField(m, num, v)
 		if err == errUnknown {
 			unknown := m.GetUnknown()
 			unknown = protowire.AppendTag(unknown, num, protowire.BytesType)
@@ -68,7 +68,7 @@
 	})
 }
 
-func unmarshalMessageSetField(m protoreflect.Message, num protowire.Number, v []byte, o UnmarshalOptions) error {
+func (o UnmarshalOptions) unmarshalMessageSetField(m protoreflect.Message, num protowire.Number, v []byte) error {
 	md := m.Descriptor()
 	if !md.ExtensionRanges().Has(num) {
 		return errUnknown
diff --git a/proto/size.go b/proto/size.go
index 11ba841..554b9c6 100644
--- a/proto/size.go
+++ b/proto/size.go
@@ -23,10 +23,13 @@
 		return 0
 	}
 
-	return sizeMessage(m.ProtoReflect())
+	return o.size(m.ProtoReflect())
 }
 
-func sizeMessage(m protoreflect.Message) (size int) {
+// size is a centralized function that all size operations go through.
+// For profiling purposes, avoid changing the name of this function or
+// introducing other code paths for size that do not go through this.
+func (o MarshalOptions) size(m protoreflect.Message) (size int) {
 	methods := protoMethods(m)
 	if methods != nil && methods.Size != nil {
 		out := methods.Size(protoiface.SizeInput{
@@ -42,52 +45,52 @@
 		})
 		return len(out.Buf)
 	}
-	return sizeMessageSlow(m)
+	return o.sizeMessageSlow(m)
 }
 
-func sizeMessageSlow(m protoreflect.Message) (size int) {
+func (o MarshalOptions) sizeMessageSlow(m protoreflect.Message) (size int) {
 	if messageset.IsMessageSet(m.Descriptor()) {
-		return sizeMessageSet(m)
+		return o.sizeMessageSet(m)
 	}
 	m.Range(func(fd protoreflect.FieldDescriptor, v protoreflect.Value) bool {
-		size += sizeField(fd, v)
+		size += o.sizeField(fd, v)
 		return true
 	})
 	size += len(m.GetUnknown())
 	return size
 }
 
-func sizeField(fd protoreflect.FieldDescriptor, value protoreflect.Value) (size int) {
+func (o MarshalOptions) sizeField(fd protoreflect.FieldDescriptor, value protoreflect.Value) (size int) {
 	num := fd.Number()
 	switch {
 	case fd.IsList():
-		return sizeList(num, fd, value.List())
+		return o.sizeList(num, fd, value.List())
 	case fd.IsMap():
-		return sizeMap(num, fd, value.Map())
+		return o.sizeMap(num, fd, value.Map())
 	default:
-		return protowire.SizeTag(num) + sizeSingular(num, fd.Kind(), value)
+		return protowire.SizeTag(num) + o.sizeSingular(num, fd.Kind(), value)
 	}
 }
 
-func sizeList(num protowire.Number, fd protoreflect.FieldDescriptor, list protoreflect.List) (size int) {
+func (o MarshalOptions) sizeList(num protowire.Number, fd protoreflect.FieldDescriptor, list protoreflect.List) (size int) {
 	if fd.IsPacked() && list.Len() > 0 {
 		content := 0
 		for i, llen := 0, list.Len(); i < llen; i++ {
-			content += sizeSingular(num, fd.Kind(), list.Get(i))
+			content += o.sizeSingular(num, fd.Kind(), list.Get(i))
 		}
 		return protowire.SizeTag(num) + protowire.SizeBytes(content)
 	}
 
 	for i, llen := 0, list.Len(); i < llen; i++ {
-		size += protowire.SizeTag(num) + sizeSingular(num, fd.Kind(), list.Get(i))
+		size += protowire.SizeTag(num) + o.sizeSingular(num, fd.Kind(), list.Get(i))
 	}
 	return size
 }
 
-func sizeMap(num protowire.Number, fd protoreflect.FieldDescriptor, mapv protoreflect.Map) (size int) {
+func (o MarshalOptions) sizeMap(num protowire.Number, fd protoreflect.FieldDescriptor, mapv protoreflect.Map) (size int) {
 	mapv.Range(func(key protoreflect.MapKey, value protoreflect.Value) bool {
 		size += protowire.SizeTag(num)
-		size += protowire.SizeBytes(sizeField(fd.MapKey(), key.Value()) + sizeField(fd.MapValue(), value))
+		size += protowire.SizeBytes(o.sizeField(fd.MapKey(), key.Value()) + o.sizeField(fd.MapValue(), value))
 		return true
 	})
 	return size
diff --git a/proto/size_gen.go b/proto/size_gen.go
index 1118460..3cf61a8 100644
--- a/proto/size_gen.go
+++ b/proto/size_gen.go
@@ -11,7 +11,7 @@
 	"google.golang.org/protobuf/reflect/protoreflect"
 )
 
-func sizeSingular(num protowire.Number, kind protoreflect.Kind, v protoreflect.Value) int {
+func (o MarshalOptions) sizeSingular(num protowire.Number, kind protoreflect.Kind, v protoreflect.Value) int {
 	switch kind {
 	case protoreflect.BoolKind:
 		return protowire.SizeVarint(protowire.EncodeBool(v.Bool()))
@@ -46,9 +46,9 @@
 	case protoreflect.BytesKind:
 		return protowire.SizeBytes(len(v.Bytes()))
 	case protoreflect.MessageKind:
-		return protowire.SizeBytes(sizeMessage(v.Message()))
+		return protowire.SizeBytes(o.size(v.Message()))
 	case protoreflect.GroupKind:
-		return protowire.SizeGroup(num, sizeMessage(v.Message()))
+		return protowire.SizeGroup(num, o.size(v.Message()))
 	default:
 		return 0
 	}